Why does ph drop when rez gets low ??

waterdawg

waterdawg

Well-Known Member
Not sure how DWC works re solution changes but when my Ph starts to drop rapidly I know its time to change my res. I dont top up very often as it seems to put things out of equilibrium. I use well water which probably is the cause. Flowering seems to be when it happens the quickest.
 
Hydroburn

Hydroburn

Well-Known Member
There is no possible way his plants are drinking so much water that the nute concentration goes from 5.8 to 4.9 in 12 hours... so that little theory can get tossed... unless he has like a little 2200ppm puddle of nutes left in the buckets or something.

random questions but... are they in 12/12 or veg, how are the roots looking, what is res temp, and are the leaves eagle clawing at all? you shouldn't let the res get low in DWC btw... besides the rapid temp/ph fluctuation, if the waterline gets low a lot the air makes the roots form into ropes.
 
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Meast21

Well-Known Member
MEANGREEN69 said:
not sure about this.. plants will drink just water and nutes when they want. if you watch your PPM's im sure there going up as the PH goes down. thats whats causing the drop in PH. i think we could use some more info, like how big is the plant? is it in flower or veg? if you have a large plant in 3 1/2 gallons it going to be sucking down water fast. if its vegging take clones to keep it going, kill it off and start a new mother from the clones. but i woulnt flower in that rez or your going to be fighting with it the whole time.use a bigger rez if your going to flower said plant. bigger res = stable PH.
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its a 5 gallon rez but only can put 3.75 gallons bc of net cup... Plant is in veg about 5 weeks from seed.... PPM has been set to 325 but has been going down regularly around 300, does this mean Im ushing too much nutes and could be my problem with ph going down ????
 
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Meast21

Well-Known Member
Hydroburn said:
There is no possible way his plants are drinking so much water that the nute concentration goes from 5.8 to 4.9 in 12 hours... so that little theory can get tossed... unless he has like a little 2200ppm puddle of nutes left in the buckets or something.

random questions but... are they in 12/12 or veg, how are the roots looking, what is res temp, and are the leaves eagle clawing at all? you shouldn't let the res get low in DWC btw... besides the rapid temp/ph fluctuation, if the waterline gets low a lot the air makes the roots form into ropes.
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In veg water temp is 65-71 and roots are crystal white.
 
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Meast21

Well-Known Member
Set ppm at 320 (rez change about 2 days ago) its now at 240... Am I over feeding ??? Is the over feeding making ph go down gradually ?? EXPERTS PLeASE
 
Hydroburn

Hydroburn

Well-Known Member
def not an expert, just a hobbyist... but ppm going down normally means your plants are hungry and you need to feed more. Not sure how big your plants are, but you might try increasing the ppm and maybe even running some cal/mag to see if the ph stabilizes. 325 is pretty light feeding esp if you are using tap water but all depends on the size of your plants and all that.

water circulation can effect ph in a way... if you have a big dense root ball and don't get any water flow through it, the ph inside the rootball can be way different than the nutes in your bucket. I had issues once because the ph of my bucket kept diving and I would keep adding ph up every day but I wasn't really mixing it very well... the root ball was dense in flower and leaching out low ph into the bucket causing the ph to constantly dive.
 
M

Meast21

Well-Known Member
Hydroburn said:
def not an expert, just a hobbyist... but ppm going down normally means your plants are hungry and you need to feed more. Not sure how big your plants are, but you might try increasing the ppm and maybe even running some cal/mag to see if the ph stabilizes. 325 is pretty light feeding esp if you are using tap water but all depends on the size of your plants and all that.

water circulation can effect ph in a way... if you have a big dense root ball and don't get any water flow through it, the ph inside the rootball can be way different than the nutes in your bucket. I had issues once because the ph of my bucket kept diving and I would keep adding ph up every day but I wasn't really mixing it very well... the root ball was dense in flower and leaching out low ph into the bucket causing the ph to constantly dive.
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I thought ppm going down meant overfeeding the plant ??
 
Alex281

Alex281

Well-Known Member
Meast21 said:
Can any expert's verify the quote above ??
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what needs to be verified? common sense should tell you that your plants are uptaking more water than nutrients, therefore, the higher nutrient concentration in a smaller volume of water = lower ph
 
superstoner1

superstoner1

Well-Known Member
Sounds like you are not using enough nutes to provide a proper pH buffer. I run 600-700 in dwc and pH stays perfect for days on end. 300-400 in a small res is not much
 
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Meast21

Well-Known Member
superstoner1 said:
Sounds like you are not using enough nutes to provide a proper pH buffer. I run 600-700 in dwc and pH stays perfect for days on end. 300-400 in a small res is not much
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WOW I need a better understanding of ppm effects on ph.... I was starting my ppm at 325 and in would slowly go down then crash after like 3-4 days to 235... 20 hours ago I did change and set at 475 and now it is about 485.... So supserstoner if ppm stays the same after rez change or close to not changing you top off with just ph'd water and no nutes or what ????
 
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Meast21

Well-Known Member
Also superstoner u say u run at 600-700 ppm, do you feed more gradually as plant matures ??? U don't run 600-700ppm in week 1 of flower and week 6 of flower ???
 
waterdawg

waterdawg

Well-Known Member
I keep notes and as SS says i run 600 range but as time passes this will start to rise with no add back. With veg things tend to stay pretty constant over the 7 days before res change but when in the throws flower the nute levels climb starting at day 5 and ph will start to drop, i can keep it around 6ish but by day seven i would have to add up daily if no res change. As i said i could add back but i try to keep it simple and my nutes are cheap relatively speaking. The first week of flower im at the 450-500 range and slowly raise if needed. Again i watch the fluctuations. I found reading the Lucas formula was great even though i dont follow the nute schedule.
 
Hydroburn

Hydroburn

Well-Known Member
Meast21 said:
20 hours ago I did change and set at 475 and now it is about 485
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keep ppm close to there for a couple days, see how ph does and watch if ppm rises or drops and by how much. In 5 gallon buckets it might take a couple days after a fresh res change to stabilize if you are using tap water... stuff is gassing off etc.
 
superstoner1

superstoner1

Well-Known Member
Meast21 said:
Also superstoner u say u run at 600-700 ppm, do you feed more gradually as plant matures ??? U don't run 600-700ppm in week 1 of flower and week 6 of flower ???
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I keep ppm same from day 1 to harvest in dwc, 600-650. I do not top off nutes or top off water, I start with 5gal and when its gets to around 1-1\2gal I change it.
 
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Detroit76

Member
My flood table runs just over 1000ppm in veg and almost 1500ppm in flower. Tap water can be almost 200ppm before you add anything. You need 500ppm for seedlings/clones. The water in a dwc system evaporates fast, leaving the nutrients behind and the ppm will increase due to the ratio of dissolved solids to the less water. Likewise your ph will lower because the salts make the water acidic.
 
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